1. Field of the Invention
The present invention relates to a method for manufacturing a monolithic semiconductor laser that can suppress fluctuation in laser properties and can improve reliability.
2. Background Art
A monolithic semiconductor laser wherein both a semiconductor laser for CD and a semiconductor laser for DVD having different emission wavelengths are formed on the same substrate has been used (e.g., refer to Japanese Patent Laid-Open No. 2000-244073 and No. 2005-109102).
A method for manufacturing a conventional monolithic semiconductor laser will be described referring to the drawings. First, as shown in FIG. 24, a buffer layer 11, a first lower clad layer 12, a first active layer 13, a first upper clad layer 40, a second upper clad layer 41, and a first contact layer 17 are formed on a GaAs substrate 10. Thereafter, a photoresist 18 is applied onto the entire surface and patterned.
Next, the buffer layer 11, the first lower clad layer 12, the first active layer 13, the first upper clad layer 40, the second upper clad layer 41, and the first contact layer 17 are etched using the photoresist 18 as a mask. Thereafter, the photoresist 18 is removed. Thereby, a semiconductor laser for CD 19 is formed as shown in FIG. 25.
Next, a buffer layer 21, a second lower clad layer 22, a second active layer 23, a third upper clad layer 24, a second etching stopper layer 25, a fourth upper clad layer 26, and a second contact layer 27 are formed on the entire surface. Then, the buffer layer 21, the second lower clad layer 22, the second active layer 23, the third upper clad layer 24, the second etching stopper layer 25, the fourth upper clad layer 26, and the second contact layer 27 are etched using photoresist as a mask. Thereby, a semiconductor laser for DVD 29 interelement-separated from the semiconductor laser for CD 19 is formed as shown in FIG. 26.
Next, as shown in FIG. 27, a photoresist 31 is applied onto the entire surface and patterned. Then, as shown in FIG. 28, the first contact layer 17, the second upper clad layer 41, and the first upper clad layer 40 of the semiconductor laser for CD 19; and the second contact layer 27 and the fourth upper clad layer 26 of the semiconductor laser for DVD 29 are simultaneously subjected to dry etching using the photoresist 31 as a mask. Thereby, first and second ridges 32 and 33 are formed on the semiconductor laser for CD 19 and the semiconductor laser for DVD 29, respectively. Thereafter, the photoresist 31 is removed as shown in FIG. 29.